Tobacco smoke is a complex mixture which includes numerous chemical compounds and particulates which to a major extent are responsible for both the enjoyment of smoking and the dangers to health in so doing. Use of tobacco products, especially smoking, is associated with increased incidence of lung and other types of cancer, emphysema, and cardiovascular disease. Less lethal adverse effects such as tooth discoloration and facial wrinkling also occur. Among the many compounds present in tobacco smoke are the purported addictive component nicotine, compounds responsible for flavor, and those either proven harmful or believed to be harmful to human health. Tobacco smoke contains chemical toxins such as carbon monoxide and hydrogen cyanide, and known carcinogens such as formaldehyde and hydrazine. Specific compounds in tobacco smoke may fall into more than one of these categories, such as those responsible for flavor. Methods for reducing the exposure of smokers to these toxic compounds without affecting the flavor of smoke while maintaining nicotine delivery has been sought for many decades.
Nicotine is an alkaloid present in tobacco and tobacco smoke and is believed to provide the addictive component. Its long-term effects on health are uncertain; nevertheless, one trend in reducing exposure to the harmful effects of tobacco is to provide smokers with alternative nicotine delivery systems, by inhalation, oral absorption, and transdermally, among other routes of administration.
The harmful effects of tobacco use, and principally cigarette smoking, derive from the delivery to the body of toxic compounds present in tobacco and volatilized during its combustion, as well as those formed as a result of combustion. These include gaseous compounds, such as carbon monoxide, hydrogen cyanide, ammonia, and formaldehyde, and others that are volatilized in tobacco smoke, such as benzene, acrolein, hydrazine, and aniline. Collectively, the solid material which may be condensed from tobacco smoke is known as tar. Several compounds in smoke and tar are classified as carcinogens: benzene, 2-naphthylamine, 4-aminobiphenyl, and the radioactive element polonium-210. Others are considered probably human carcinogens, such as formaldehyde, hydrazine, N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosopyrrolidine, benzo[a]pyrene, N-nitrosodiethanolamine, and cadmium. Further compounds in tobacco smoke have been proven to be animal carcinogens. While the carcinogenic potential of these tobacco smoke components has never been tested directly in humans, a cause-and-effect relationship between smoking and the aforementioned adverse effects has been strongly established through epidemiologic studies.
Numerous methods and devices to reduce or remove toxic components from tobacco and tobacco have been proposed and constructed. In general, a porous filter is provided as a first line trap for harmful components, interposed between the smoke stream and the mouth. This type of filter, often composed of cellulose acetate, both mechanically and by adsorption, traps a certain fraction of the tar present in smoke. This type of filter is present on most cigarettes available, yet it allows a significant amount of harmful compounds to pass into the mouth. Epidemiological data connects use of filtered cigarettes with adverse health effects.
An improvement in the effectiveness afforded by a mechanical-type filter such as those described above may be provided by including means for chemically trapping disagreeable and harmful components present in smoke. For example, U.S. Pat. No. 5,076,294 provides a filter element containing an organic acid, such as citric acid, which reduces the harshness of the smoke. A significant body of art focuses on removing formaldehyde, a prevalent component of tobacco smoke with an established and adverse toxicological profile. U.S. Pat. No. 4,300,577 describes a filter comprising an absorptive material plus an amine-containing component which removes aldehydes and hydrogen cyanide from tobacco smoke. U.S. Pat. No. 5,009,239 describes a filter element treated with polyethyleneimine modified with an organic acid, to remove aldehydes from tobacco smoke. U.S. Pat. No. 4,246,910 describes a filter impregnated with alkali ferrate compounds, or activated carbon or alumina impregnated with potassium permanganate, for removing hydrogen cyanide from tobacco smoke. Control of the delivery of tar, nicotine, formaldehyde and total particulate matter was afforded by a filter element containing zinc thiocyanate, sarcosine hydrochloride, zinc chloride, ferrous bromide, lithium bromide, or manganese sulfate, as describe in U.S. Pat. No. 4,811,745. Inclusion of L-ascorbic acid in a filter material to remove aldehydes is disclosed in U.S. Pat. No. 4,753,250. U.S. Pat. No. 5,060,672 also describes a filter for specifically removing aldehydes, such as formaldehyde, from tobacco smoke by providing a combination of an enediol compound, such as dihydroxyfumaric acid or L-ascorbic acid, together with a radical scavenger of aldehydes, such as oxidized glutathione or urea, or a compound of high nucleophilic activity, such as lysine, cysteine, 5,5-dimethyl-1,3-cyclohexanedione, or thioglycolic acid. Such filters, however, have not been shown to reduce the harmful effects of tobacco smoke, and have yet to demonstrate adequate consumer acceptance or commercial viability. Furthermore, many of the agents used in the above-mentioned filters, such as organic acids, will trap nicotine and interfere with its delivery to the smoker.
As used throughout this application, the terms nucleophile and nucleophilic refer to a negative ion or neutral molecule, such as an amino group or primary or secondary amine, that brings an electron pair into a chemical reaction with another molecule or positive ion, called an electrophile which is capable of accepting the electron pair, such as an active carbonyl group. Nucleophilic compounds will chemically react with compounds bearing active carbonyl groups, such as aldehydes, anhydrides, activated ketones, and active esters.
Smokeless tobacco includes tobacco products which are used by methods other than smoking, for instance, as snuff and chewing tobacco. Toxic products present in tobacco also enter the body by these methods of using tobacco which do not involve combustion, and these products are also associated with numerous adverse sequelae of tobacco use.
Contrary to the above-cited prior art in which nucleophilic compounds incorporated in a filter were used to trap aldehyde-type toxins in tobacco smoke, it has been discovered that the nucleophilic toxins present in tobacco and tobacco smoke may be removed from tobacco and tobacco smoke by agents, or filters derivatized with chemical moieties comprising these agents, which chemically trap nucleophilic compounds. Tar, mutagens, and known carcinogens present in tobacco and tobacco smoke may be effectively removed by these agents or filters comprising these agents which chemically traps nucleophilic toxins, without affecting the nicotine and flavor components of smoke. Furthermore, agents which trap nucleophilic toxins may be incorporated into air filters to remove tobacco-derived toxins from room air, to reduce exposure to second-hand (sidestream) smoke.